case mouth expansion necessary?

[sandman]

been handloading for rifle about 5-6 years, and i'm ready to make the step to loading for my 40 s&w (h&k usp compact--i checked with the manufacturer and the case head is fully supported). i plan on using jhp's, either from nosler or speer.

is flaring the case mouth necessary when using jacketed bullets? it seems like a lot more stress on the brass (as well as an extra step on my single stage press).

if so, it might be time to start looking for a progressive press...